Antioxidant peptides are promising candidates for mitigating oxidative skin damage, but their topical application is often limited by poor skin permeability and an incomplete understanding of how permeability-enhancing modifications affect biological activity. In this study, we designed a focused series of antioxidant peptides by sequence truncation and N-terminal palmitoylation to investigate how lipid modification regulates skin delivery, supramolecular assembly, antioxidant performance, and cellular compatibility. Four parent peptides and their C16-modified derivatives were synthesized and systematically evaluated. Palmitoylation markedly increased peptide hydrophobicity and promoted self-assembly, as evidenced by reduced critical aggregation concentrations and the formation of distinct supramolecular structures, including liquid-like coacervates and micelle-like assemblies. In vitro Franz diffusion studies using porcine skin showed that C16 modification substantially enhanced skin permeation and retention, with the improvement mainly associated with increased skin partitioning rather than accelerated diffusion. However, the biological consequences of lipidation were strongly sequence- and dose-dependent. Although selected lipopeptides improved intracellular ROS suppression, cytoprotection against H2O2-induced oxidative injury, and fibroblast migration, palmitoylation did not universally enhance chemical radical-scavenging activity or endogenous antioxidant responses. In several cases, unmodified peptides showed stronger SOD- and GSH-related regulation, whereas highly hydrophobic derivatives exhibited reduced biocompatibility at elevated concentrations. These findings reveal a permeability–bioactivity trade-off in palmitoylated antioxidant peptides and demonstrate that optimizing transdermal peptide antioxidants requires balancing hydrophobicity, self-assembly, skin partitioning, and cellular safety. This work provides a systematic framework for designing lipid-modified antioxidant peptides for topical skin protection and repair.

The linker region of lipopeptides has demonstrated considerable potential in modulating their antibacterial activity. However, a clear consensus regarding the influence of link length on their physicochemical properties and biological activities remains elusive. To address this, we designed a series of octanoyl lipopeptides, C8Gn(VVKK)2V-NH2 (n=1-3), with varying glycine linker length. Altering the linker length led to distinct physicochemical properties and self-assembly behaviors, enabling an investigation into the structure-property-function relationship. Among the series, C8G(VVKK)2V-NH2 exhibited the lowest surface activity and consequently the weakest antibacterial efficacy. In contrast, C8G2(VVKK)2V-NH2 and C8G3(VVKK)2V-NH2 displayed high surface activity, and self-assembled into micelles above their critical aggregation concentrations (CACs). Notably, these micelles disassembled upon dilution, facilitating high antibacterial activity through bacterial membrane disruption. Conversely, the micelles formed by C8G(VVKK)2V-NH2 were exceptionally stable, allowing them to attach on bacterial surface but not permeate bacterial membrane, leading to low antibacterial activity. Thus, we demonstrate that the incorporating glycine linkers modulates the self-assembly behavior of octanoyl lipopeptides: increased linker length promotes micelle disassembly and enhances antibacterial activity. This study offers deeper insights into the antibacterial mechanisms of self-assembling lipopeptides, facilitating the future exploration of their biomedical applications.

Antioxidant peptides are promising candidates for mitigating oxidative skin damage, but their topical application is often limited by poor skin permeability and an incomplete understanding of how permeability-enhancing modifications affect biological activity. In this study, we designed a focused series of antioxidant peptides by rational sequence engineering and N-terminal C16 conjugation to investigate how this modification influences skin delivery, supramolecular assembly, antioxidant performance, and cellular compatibility. Four designed antioxidant peptides and their C16-modified derivatives were synthesized and systematically evaluated. N-terminal C16 conjugation markedly increased peptide hydrophobicity and promoted self-assembly, as evidenced by reduced critical aggregation concentrations (CACs) and the formation of distinct supramolecular structures, including liquid-like coacervates and micelle-like assemblies. In vitro Franz diffusion studies using porcine skin showed that C16 modification substantially enhanced skin permeation and retention, with the improvement mainly associated with increased skin partitioning rather than accelerated diffusion. However, the biological consequences of lipidation were strongly sequence- and dose-dependent. Although selected C16-conjugated peptides improved intracellular ROS suppression, cytoprotection against H2O2-induced oxidative injury, and fibroblast migration, N-terminal C16 conjugation did not universally enhance chemical radical-scavenging activity or endogenous antioxidant responses. In several cases, unmodified peptides showed stronger SOD- and GSH-related regulation, whereas highly hydrophobic derivatives exhibited reduced biocompatibility at elevated concentrations. These findings reveal a permeability-bioactivity trade-off in N-terminal C16-conjugated antioxidant peptides and demonstrate that optimizing transdermal peptide antioxidants requires balancing hydrophobicity, self-assembly, skin partitioning, and cellular safety. This work provides a systematic framework for designing lipid-modified antioxidant peptides for topical skin protection and repair.

Bacterial diseases mainly caused by Vibrio species pose a serious threat to shrimp aquaculture and lead to the sudden mass mortalities and huge economics losses. The unfavorable side effects and emergence of superbugs in traditional antibiotic treatment makes development of excellent antibacterial agents especially urgent. Antimicrobial peptides (AMPs), which usually have high antibacterial activity and low potential to induce bacterial resistance, are considered as the promising alternatives to conventional antibiotics. However, their anti-Vibrio mechanisms have not yet reached a consensus. In this study, a pathogenic Vibrio strain was isolated from the cultured shrimp and was identified as Vibrio parahaemolyticus UPC-1 (V. Parahaemolyticus UPC-1). Studies showed that G3 efficiently protected shrimp from V. Parahaemolyticus UPC-1 infection through two independent ways. In one way, G3 balanced the bacterial community of shrimp gut by selectively killing the pathogenic Vibrio bacteria. In the other way, G3 markedly reduced the robust inflammation effects induced by Vibrio infection. Such efficient anti-Vibrio activity of G3 endows it great potential in the treatment of Vibrio infections in shrimp aquaculture.

The self-assembling morphologies of proteins, nucleic acids, and peptides are well correlated with their functioning in biological systems. In spite of extensive studies for the morphologies regulating, the directional control of the assembly morphology structure for the peptides still remains challenging. Here, the directional structure control of a bola-like peptide Ac-KIIF-CONH2 (KIIF) was realized by introducing different amount of acetonitrile to the system. The morphologies were characterized by transmission electron microscopy (TEM) and atomic force microscopy (AFM), and the secondary structure was evaluated by circular dichroism (CD) and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that the introducing of different amount of acetonitrile has significantly tuned the hydrophobic interactions amongst the side chains, thus affecting the self-assembling morphologies. As acetonitrile content increased, the assemblies changed from nanotubes to helical/twisted ribbons and then to thin fibrils, with a steady decrease in the width. In contrast, the assemblies changed from thin fibrils to helical/twisted ribbons, and then to matured nanotubes, exhibiting a steady increase in the width with peptide concentration increasing. Complementary molecular dynamics (MD) simulations demonstrated the important role of acetonitrile in controlling the hydrophobic interactions, providing microscopic evidence for the structure transition process. We believe such observations provide important insights into the design and fabrication of functional materials with controlled shape and size.

Antibacterial peptides (ABPs) have been recognized as promising alternatives to conventional antibiotics due to their broad antibacterial spectrum, high antibacterial activity, and low possibility of inducing bacterial resistance. However, their antibiofilm mechanisms have not yet reached a consensus. In this study, we investigated the antibiofilm activity of a short helical peptide G3 against Staphylococcus epidermidis, one of the most important strains of medical device contamination. Studies show that G3 inhibits S. epidermidis biofilm formation in a variety of ways. In the initial adhesion stage, G3 changes the properties of bacterial surfaces, such as charges, hydrophobicity, and permeability, by rapidly binding to them, thus interfering with their initial adhesion. In the mature stage, G3 prefers to target extracellular polysaccharides, leading to the death of outside bacteria and the disruption of the three-dimensional (3D) architecture of the bacterial biofilm. Such efficient antibiofilm activity of G3 endows it with great potential in the treatment of infections induced by the S. epidermidis biofilm.

The controlled peptide self-assembly and disassembly are not only implicated in many cellular processes but also possess huge application potential in a wide range of biotechnology and biomedicine. β-sheet peptide assemblies possess high kinetic stability, so it is usually hard to disassemble them rapidly. Here, we reported that both the self-assembly and disassembly of a designed short β-sheet peptide IIIGGHK could be well harnessed through the variations of concentration, pH, and mechanical stirring. Microscopic imaging, neutron scattering, and infrared spectroscopy were used to track the assembly and disassembly processes upon these stimuli, especially the interconversion between thin, left-handed protofibrils and higher-order nanotubes with superstructural right-handedness. The underlying rationale for these controlled disassembly processes mainly lies in the fact that the specific His-His interactions between protofibrils were responsive to these stimuli. By taking advantage of the peptide self-assembly and disassembly, the encapsulation of the hydrophobic drug curcumin and its rapid release upon stimuli were achieved. Additionally, the peptide hydrogels facilitated the differentiation of neural cells while maintaining low cell cytotoxicity. We believe that such dynamic and reversible structural transformation in this work provides a distinctive paradigm for controlling the peptide self-assembly and disassembly, thus laying a foundation for practical applications of peptide assemblies.

The decellularized tilapia skin (dTS) has gained significant attention as a promising material for tissue regeneration due to its ability to provide unique structural and functional components that support cell growth, adhesion, and proliferation. However, the clinical application of dTS is limited by its low mechanical strength and rapid biodegradability. Herein, we prepare a novel RGD (arginine-glycine-aspartic acid) functionalized dTS scaffold (dTS/RGD) by using transglutaminase (TGase) crosslinking. The developed dTS/RGD scaffold possesses excellent properties, including a medium porosity of ∼59.2%, a suitable degradation rate of approximately 80% over a period of two weeks, and appropriate mechanical strength with a maximum tensile stress of ∼46.36 MPa which is much higher than that of dTS (∼32.23 MPa). These properties make the dTS/RGD scaffold ideal for promoting cell adhesion and proliferation, thereby accelerating skin wound healing in a full-thickness skin defect model. Such an enzymatic cross-linking strategy provides a favorable microenvironment for wound healing and holds great potential for application in skin regeneration engineering.

The mechanical properties and bioactive motif densities of extracellular matrix materials play crucial roles in regulating cell behaviors, such as cell adhesion, migration, proliferation, and differentiation. However, current studies on cellular responses to ECM predominantly concentrated on polymer hydrogels featuring a single factor, such as the mechanical strength, the types of bioactive motifs, and the morphology of the polymers. This limited focus may overlook the complex interplay of multiple factors. Here, we developed dual gradient peptide Q3GT-I3K hydrogels with tunable mechanical strength (0.3-4.0 kPa) and different density of bioactive motif (0.45-3.67 mM) by enzymatic crosslinking. These hydrogels can mimic the viscoelasticity of natural soft tissues. The properties of mechanical strength and cell responsive motif density could be controlled by modulating the proportion of the substrates in the enzymatic reaction. MC3T3 cells significantly differentiated into osteoblasts after seeded on the Q3GT-I3K hydrogel (2.8 kPa, 1.83 mM Q3GT) for 21 days, identifying from the elevated expression of alkaline phosphatase and substantial calcium nodule formation. Importantly, the engineered hydrogels exert a synergistic effect on the cell behaviors such as early adhesion, late proliferation, and differentiation of MC3T3-E1 cells. This paper introduces a new strategy for designing tissue engineering scaffold materials with specific functions.

With the rising global incidence of melanoma, new anti-melanoma drugs with low-inducing drug resistance and high selectivity are in urgent need. Inspired by the physiological events in which fibrillar aggregates formed by amyloid proteins are toxic to normal tissues, we here rationally design a tyrosinase responsive peptide, I4K2Y* (Ac-IIIIKKDopa-NH2). Such peptide self-assembled into long nanofibers outside the cells, while it was catalyzed into amyloid-like aggregates by tyrosinase which was rich in melanoma cells. The newly formed aggregates concentrated around the nucleus of melanoma cells, blocking the exchange of biomolecules between the nucleus and cytoplasm and finally leading to cell apoptosis via the S phase arrest in cell cycle distribution and dysfunction of mitochondria. Furthermore, I4K2Y* effectively inhibited B16 melanoma growth in a mouse model but with minimal side effects. We believe that the strategy of combining the usage of toxic amyloid-like aggregates and in-situ enzymatic reactions by specific enzymes in tumor cells will bring profound implications for designing new anti-tumor drugs with high selectivity.

Critical-size bone defects are imposing a substantial biomedical burden. Despite being long regarded as a potential approach to mitigate this burden or an alternative to bone grafts, bone tissue engineering (BTE) has virtually not proceeded to widespread clinical practices. In the BTE field, it is highly required to find a facile method to prepare active scaffolds with tailored biological functions. Here, we immobilized cell adhesive RGD motifs onto gelatin sponge (GS) scaffolds through enzymatic linking. On the basis of the resulting RGD-functionalized GS (RGD/GS) scaffolds, we developed a new and convenient strategy for bone defect repair, in which the scaffolds were first used to recruit mesenchymal stem cells (MSCs) from skeletal muscle, immediately followed by their engraftment into bone defect. We demonstrated significantly enhanced host cells homing into RGD/GS scaffolds as a result of specific RGD-integrin interactions, and the recruited host cells showed a strong osteogenic differentiation potential. After ectopic implantation of cell-laden RGD/GS scaffolds into critical-size mouse bone defects, marked bone tissue regeneration occurred. The presented strategy not only provides an agile route for the preparation of bioactive scaffolds and the construction of osteoinductive bone-graft substitutes, but also avoids or minimizes the complicated and laborious cell isolation, in vitro expansion and cell seeding procedures used in the conventional BTE.

Lipopeptides have become one of the most potent antibacterial agents, however, there is so far no consensus about the link between their physic-chemical properties and biological activity, in particular their inherent aggregation propensity and antibacterial potency. To this end, we here de novo design a series of lipopeptides (CnH(2n-1)O-(VVKK)2V-NH2), in which an alkyl chain is covalently attached onto the N-terminus of a short cationic peptide sequence with an alternating pattern of hydrophobic VV (Val) and positively charged KK (Lys) motifs. By varying the alkyl chain length (ortho-octanoic acid (C8), lauric acid (C12), and palmitic acid (C16)), the lipopeptides show distinct physicochemical properties and self-assembly behaviors, which have great effect on their antibacterial activities. C8H15O-(VVKK)2V-NH2, which contains the lowest hydrophobicity and surface activity has the lowest antibacterial activity. C12H23O-(VVKK)2V-NH2 and C16H31O-(VVKK)2V-NH2 both have high hydrophobicity and surface activity, and self-assembled into long nanofibers. However, the nanofibers formed by C12H23O-(VVKK)2V-NH2 disassembled by dilution, resulting in its high antibacterial activity via bacterial membrane disruption. Comparatively, the nanofibers formed by C16H31O-(VVKK)2V-NH2 were very stable, which can closely attach on bacterial surface but not permeate bacterial membrane, leading to its low antibacterial activity. Thus, the stability other than the morphologies of lipopeptides' nanostructures contribute to their antibacterial ability. Importantly, this study enhances our understanding of the antibacterial mechanisms of self-assembling lipopeptides that will be helpful in exploring their biomedical applications.

Peptide molecules can self-assemble to form one-dimensional nanostructures, and the formation of these structures is closely related to the delicate balances of different non-covalent interactions. These non covalent interactions can be finely tuned by changing the molecular structure and the external conditions. Among them, the introduction of organic solvents to peptide based systems is a simple and effective way for regulating the aggregate structure. In this study, we used three bola-form hexapeptide molecules Ac-KI4K-NH2, Ac-RI4R-NH2 and Ac-HI4H-NH2 with different hydrophilic amino acids as models to investigate the effect of methanol on the morphology of the self-assemblies. The self-assembly behavior of these peptides in methanol was thoroughly investigated by a combination of transmission electron microscopy (TEM), atomic force microscopy (AFM), circular dichroism spectroscopy (CD), and Fourier transform infrared spectroscopy (FTIR). The results demonstrated that both the solvent methanol and the hydrophilic amino acids in the peptides have a great impact on the morphologies of the self-assemblies. Ac-KI4K-NH2 self-assembled into thin nanofibers in methanol. In contrast, Ac-RI4R-NH2 formed a monolayer helical ribbons with an obvious dynamic process initiating from thin twist nanofibers, then thin helical ribbons, and finally evolved to wide helical ribbons. The dominant nanostructures for Ac-HI4H-NH2 were multi-layer flat ribbons but with a narrower width. These morphologies formed in methanol were significantly different from those formed in water, due to the weakened electrostatic, hydrogen bonding, and hydrophobic interactions between peptides or peptides and methanol. The introduction of methanol creates a completely hydrophobic environment and changes the non-covalent interactions within 13-sheets, thus resulting a thin width. A gel phase with superior viscoelasticity was formed by Ac-KI4H-NH2 in methanol and it may have applications in various fields of chemistry, biomedicine, environment and electricity. These results can help us understand the roles of organic solvents in controlling the delicate balance of different non-covalent interactions as well as the final aggregate morphologies and may benefit further research in establishing the relationship among peptide solvent, peptide molecular structure, and the final aggregate morphology. (C) 2022 Elsevier B.V. All rights reserved.

A series of functional biomaterials with different sizes and morphologies can be constructed through self-assembly, among which amphiphilic peptide-based materials have received intense attention. One main possible reason is that the short amphiphilic peptides can facilitate the formation of versatile materials and promote their further applications in different fields. Another reason is that the simple structure of amphiphilic peptides can help establish the structure-function relationship. This review highlights the recent advances in the self-assembly of two typical peptide species, surfactant-like peptides (SLPs) and peptides amphiphiles (PAs). These peptides can self-assemble into diverse nanostructures. The formation of these different nanostructures resulted from the delicate balance of varied non-covalent interactions. This review embraced each non-covalent interaction and then listed the typical routes for regulating these non-covalent interactions, then realized the morphologies modulation of the self-assemblies. Finally, their applications in some biomedical fields, such as the stabilization of membrane proteins, templating for nanofabrication and biomineralization, acting as the antibacterial and antitumor agents, hemostasis, and synthesis of melanin have been summarized. Further advances in the self-assembly of SLPs and PAs may focus on the design of functional materials with targeted properties and exploring their improved properties.

Objective As for the unique properties of good biocompatibility and excellent optical performance, silica nanotubes have shown potential applications in different fields. The properties of the silica nanotubes were well correlated with their size and morphologies. In order to prepare silica nanotubes with much larger size and expand their applications in different fields, this study selected wide peptide nanotubes as templates for biomimetic synthesis of silica materials. Methods In order to obtain silica nanotubes with relative large size, here we prepared silica nanotubes by using wide nanotubes (with diameters of approximately 40 nm) self-assembled by the bola peptide Ac-KI3VK-CONH2 as templates through a biomimetic mineralization route. The stability of the peptide nanotubes was firstly investigated and the results demonstrated that these nanotubes can be easily destroyed by dilution, addition of organic solvents, or changing the solution pH value, showing poor stability. Then, we chose methyl n-silicate (TMOS) with fast reaction rate as the precursor to prepare silica nanomaterials and systemically explored the influence of different factors on the size and morphology of the silica nanotubes. Results The results demonstrated that the ideal condition for preparing silica nanotubes with uniform shape and size was using TMOS as precursor and keeping its concentration at 1.11%-3.33% (v/v) under neutral or weak alkaline conditions. Conclusion This work successfully prepared silica nanotubes with relative large diameter by using self-assemblies formed by a bola peptide as templates and silicon source with fast reaction rate, which is of great significance and may expand the applications of wide silica nanotubes in different fields.

In order to explore the application of nano-medication system of the multiple antibacterial nanometer in the treatment of otitis media, the tanshinone IIA/nano-silver composite gel was used as an example for researches in this study. The tanshinone IIA/silver nanocomposite gel was prepared using the formation principle of polymer precipitation of the in situ gel, and the obtained product was characterized and detected by ultraviolet spectrophotometry, high-performance liquid chromatography, and infrared spectroscopy. A model of guinea pig with otitis media was prepared, and all objects were treated with ofloxacin ear drops, tanshinone IIA, nano-silver, and the composite gel of tanshinone IIA and nano-silver for treatment, respectively, to observe the changes in bacterial culture, inflammatory factors, and tissue structure. The results of three methods showed that the composite gel was prepared successfully. The number of bacterial colonies in tanshinone IIA, nano-silver, and composite gel of tanshinone IIA and nano-silver was significantly lower than that in the model group (P ≤ 0.05), and the levels of TNF-α and IL-8 in the group treated with the composite gel of tanshinone IIA and nano-silver decreased significantly. In addition, the number of otitis cells in the group treated with the composite gel of tanshinone IIA and nano-silver was significantly reduced. The composite of tanshinone IIA and nano-silver had a significant effect on the treatment of otitis media, and the therapeutic effect was obviously better than that of tanshinone IIA or nano-silver alone. This experiment provided a new idea for the organic combination of more active ingredients of traditional Chinese medicine and inorganic nano-materials, and also defined a new direction for the treatment of otitis media.

Though the function of peptide based nanotubes are well correlated with its shape and size, controlling the dimensions of nanotubes still remains a great challenge in the field of peptide self-assembly. Here, we demonstrated that the shell structure of nanotubes formed by a bola peptide Ac-KI3VK-NH2 (KI3VK, in which K, I, and V are abbreviations of lysine, isoleucine, and valine) can be regulated by mixing it with the salt sodium tartrate (STA). The ratio of KI3VK and STA had a great impact on shell structure of the nanotubes. Bilayer nanotubes can be constructed when the molar ratio of KI3VK and STA was less than 1:2. Both the two hydroxyls and the negative charges carried by STA were proved to play important roles in the bilayer nanotubes formation. Observations of different intermediates provided obvious evidence for the varied pathway of the bilayer nanotubes formation. Based on these experimental results, the possible mechanism for bilayer nanotubes formation was proposed. Such a study provides a simple and effective way for regulating the shell structure of the nanotubes and may expand their applications in different fields.

Although it is well-known proteins and their complexes are hierarchically organized and highly ordered structures, it remains a major challenge to replicate their hierarchical self-assembly process and to fabricate multihierarchical architectures with well-defined shapes and monodisperse characteristic sizes via peptide self-assembly. Here we describe an amphiphilic short peptide Ac-I3GGHK-NH2 that first preassembles into thin, left-handed β-sheet nanofibrils, followed by their ordered packing into right-handed nanotubes. The key intermediate morphology and structures featuring the hierarchical process are simultaneously demonstrated. Further mechanistic exploration with the variants Ac-I3GGGK-NH2, Ac-I3GGFK-NH2, and Ac-I3GGDHDK-NH2 reveals the vital role of multiple His-His side chain interactions between nanofibrils in mediating higher-order assembly and architectures. Altogether, our findings not only advance current understanding of hierarchical assembly of peptides and proteins but also afford a paradigm of how to take advantage of side chain interactions to construct higher-order assemblies with enhanced complexities.

The development of novel hemostatic agents with distinct modes of action from traditional ones remains a formidable challenge. Self-assembling peptide hydrogels have emerged as a new hemostatic material, not only because of their inherent biocompatibility and biodegradability but also their designability. Especially, rational molecular design can make peptides and their hydrogelation responsive to biological cues. In this study, we demonstrated that transglutaminase-catalyzed reactions not only occurred among designed short peptide I3QGK molecules but also between the peptide and a natural polysaccharide O-carboxymethyl chitosan. Because Factor XIII in the blood can rapidly convert into activated transglutaminase (Factor XIIIa) upon bleeding, these enzymatic reactions, together with the electrostatic attraction between the two hemostatic agents, induced a strong synergetic effect in promoting hydrogelation, blood coagulation, and platelet adhesion, eventually leading to rapid hemostasis. The study presents a promising strategy for developing alternative hemostatic materials and methods.